Fluid operated clamping device



May 11, 1954 .1. vERDERBl-:R

FLUID OPERATED CLAMPING DEVICE 4 Sheets-Sheet l Filed July 27, 195o IN VEN TOR. EPH vakmensen.

LI llhnnl I lll BY FNS. 2 5 ATTO RNEY J. VERDERBER 2,678,072

FLUID OPERATED CLAMPING DEVICE 4 Sheets-Sheet 2 May 11, 1954 Filed July 27, 1950 ATTOi RN EY.

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FLUID OPERATED CLAMPING DEVICE Filed July 27, 1950 4 Sheets-Sheet 3 10 115 wm 5 /1l g 14. L 7

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. INVENTOR. JosEm-s VERDERBER ATTORNEY.

May 11, 1954 .1. VERDERBER 2,578,072

FLUID OPERATED CLAMPING DEVICE Filed July 27, 1950 4 Sheets-Sheet 4 5 l 17 1 En 88 JOSEPH Vlgve'aea www@ ATTORNEY.

FIG; 9

Patented May 11, 1954 UNITED STATES TENT OFFICE The present invention relates to clamping devices and more particularly to a fluid operated clamping device such as a jig for holding workpieces during machining operations.

This application is a continuation-impart of my copending application, Serial No. 162,557, liled May 17, 1950, now Patent No. 2,663,339, wherein are disclosed and claimed certain features of the invention also shown and described herein.

I have found that in utilizing the clamping device described in my said copending application, certain disadvantages result from the fact that air, which is a compressible uid, is used as the sole medium for actuating the device.

The present application describes a clamping device which is an improvement upon that disclosed in said copending application, in that it is actuated by a combination of a compressible iiuid, such as air, and a non-compressible fluid, such as oil. I thereby obtain more favorable operating characteristics in the device and overcome the disadvantages which flow from using solely a compressible fluid medium.

It is a primary object of my invention to provide a quick-acting clamping device which is actuated by uid pressure.

Another object of my invention is to provide a :duid operated clamping device which will maintain a uniform clamping action irrespectively of iiuctuations in or failure of pressure.

Still another object of my invention is to provide a clamping device which is semi-automatic in operation, requiring only control by the operator.

Other objects and advantages of the invention will be apparent during the course of the following description. i

In the accompanying drawings, forming a part of this specification, and in which like numerals are employed to designate like parts throughout the same,

Fig. 1 is a top plan view of a clamping jig embodying the features of my invention.

Fig. 2 is a front elevation of the same.

Fig. 3 is a fragmentary cross-sectional view on an enlarged scale, taken as indicated by line 3 3 on Fig. 2.

Fig. 4 is an enlarged fragmentary cross-sectional view, taken as indicated by line 4 4 on Fig. 2.

Fig. 5 is an enlarged fragmentary cross-sectional view, taken on line 5 5 of Fig. 1, and showing certain details of the valve structure.

Fig. 6 is an enlarged fragmentary cross-sectional view taken on line 6 6 of Fig. 2 and showing the valve stem in neutral position.

Fig. 7 is a view similar to Fig. 6, but showing the position of the valve stem when it is desired to release the clamp.

Fig. 8 is a cross-sectional view, taken substantially as indicated by line 8 8 of Fig. 4 and showing the cylinder closing plug in plan.

Fig. 9 is a fragmentary cross-sectional view of the device showing the by-pass channels to the check valve, the cutting plane being indicated at line 9 9 of Fig. 8.

Referring more particularly to the drawings, the clamping device is seen to comprise a base portion I having formed integrally therewith four spaced embossments 2 in which are mounted vertically extending standards 3 to which are threadedly secured a top plate P, which is indicated in broken line outline.

The plunger assembly Extending vertically from the base I and integrally formed therewith is an embossment 4 which is bored as at 5 to form a cylinder in which is slidably mounted a plunger 6. The plunger 6 is provided with a longitudinal bore 'I which is tapped to threadedly receive a plug 8, for a purpose to be described hereinafter. The bore 'I is counterbored, as at 9, to form a socket which may be utilized for holding a locating pin or the like for accurately positioning the workpiece which is to be clamped. The locating pin may be secured by a set screw ID which threadedly engages a radially extending bore I I in the wall of the plunger.

The opposite end of the plunger 6 is counterbored as at I2 to form a cylindrical cavity or chamber I3 having a closed upper end I4.

Disposed within the cavity I3 is a stationary divider I5 which is substantially in the form of a piston having a head I6 from which depends an integral rod or stem I1. The head is provided with a circumferential recess I8 which serves to retain an O-ring I9 which has wiping engagement with the wall of the cavity I3.

The stem projects downwardly through a plug 20 which is threadedly secured to the lower end of the plunger 6. The plug has an annular cavity 2l which serves to contain an oil seal 22 which encircles the stem I'I. For convenience in effecting assembly of the plug to the plunger, spaced Spanner openings 23 are provided in the plug 20.

The stem I 'I has an extension 24 of reduced diameter which projects through a cap 25 which is secured to the underside 46 of the base I by means of screws 26. The stem terminates in a threaded portion 2l which receives a nut 28 so as to secure the stem against displacement relatively to the cap 25.

The divider I5 has an axial closed-end bore 29 which terminates a short distance above the end of the stem extension 24. The bore 29 is counterbored as at 30, which counterbore extends through the head I6 and the stem I'I to a point near the end of bore 29 thereby forming a shoulder BI. A tube 32 having an internal diameter equal to that of bore 29 and having an 3 external diameter less than that of bore 39, is axially disposed in the bore 30, it being secured against the shoulder 3| by means of a hollow set screw 33, which is threadedly secured in the bore 39 and abuts the upper end of the tube 32. A second hollow set screw 34 serves as a locking screw. The screws 33 and 34 serve as extensions of the bore 29 and a ring gasket 35 is interposed between the screws in order to prevent leakage of uid around the threads. i

The bore of the tube 32 thus provides an extension of the bore 29 of the divider I5,` which bore communicates with a portion A of the chamber I3 which lies above the head |6. rThe tube 32 also deiines an annular passageway 95 in the stem I'I, which passageway communicates with a portion B of the chamber I3, which underlies the head I6, by means of a diametrical opening 3? which is provided in the stem I'I.

The cap 25 which iits snugly on the extension 24 of the stem, has a channel or passageway 38 formed therein which communicates with the upper face 39 0f the cap and then extends radially or laterally to the bore 49 of the Vcap 25 where it communicates with a radial opening 4I in stem Il which leads to the bore 29. Another channel 42 which is 180 degrees removed from channel 38 extends downwardly from the face 39 of cap 25 and then laterally to the bore 49, where it communicates with a radial opening 49 in the stein Which is located above the shoulder 3| and therefore leads to the annular passageway 35 in the bore 39 of the stem.

In order to maintain proper registry between the radial openings 4| and 43 in the stem extension 24 and the channels 38 and 42 respectively in the cap 25, the bore 48 of the cap is provided with a longitudinal recess or keyway 44 which slidably receives a key 45 which is secured to the stemrextension 24.

The piston assembly The underside 46 of the base has a vertically extending opening 4'I therein which is in registry with the channel 42 in cap 25 and communicates with a horizontally extending transverse channel 48 which is provided in the body portion 49 of the clamping device and leads to the exterior thereof.

The body 49 is provided with two spaced horizontally extending closed-end bores'58 which form cylinders and which are counterbored to form larger cylinders and annular shoulders 52. Each cylinder 5| has slidably mounted therein a movable piston 53 having an integral stem i or rod 54 which is slidably received in the cylinder or bore 59. Axially spaced pistonrings 55 are Ymounted on the piston so as to have wiping engagement with'the wall of cylinder 5i and thereby prevent leakage of fluid past the piston. The stem 54 projects through a sealing ring 56 which is threadedly secured in the Ybore 5| in abutment with the shoulder 52. The sealing ring Vis provided with an annular recess 5l' in which is retained an O-ring 58 which encircles the stem 54. Another O-ring 59 serves to prevent leakage around the threads of the sealing ring 56.

Vertical channels 93 lead from the passageway 48 to the bores or cylinders 5|.

Surmounting the piston 53 is a flat spring 58 which is secured to the piston by means of a washer 6| and screwl 62. Underlying and cushioning the spring is a resilient ring 63. Y

/A cap 64 having an annular embossment 55 serves to close the open end of cylinder 5E and is secured to the body by means of screws 66. The embossment v65 is recessed as at 5'! to provide clearance for the head of the screw 62 and the embossment is further recessed or slotted radially thereof to provide a channel 63 which communicates with a channel 69 formed in the body. The channel 69 communicates with a transverse channel 'I8 which leads to the exterior of the body for a purpose which will be fully described hereinafter.

The piston 53 partitions the cylinder 5I into two portions. A portion C lying between the piston and cap 64, and a portion D disposed between the piston and sealing ring 56.

The check'V calce The cylinders 59 are intersected by a transverse channel 'II which communicates with the bore l2 of a check valve housing '|3. The vbore l2 is counterbored as at I4 toreceive a cylinder bushing 'I5 in which is slidably mounted a piston .19 having an integral depending stem TI. An O-ring 'I8 encircles the piston and has wiping engagement with the bushing 15. The bore 'i4 is closed by means of a cap 'I9 which is threadedly secured therein.

The top of the piston is tapered or conical in form and a free space S is left between the cap i9 and the bushing 15, into which space, the conical portion of the piston I6 can project for a purpose to be described hereinafter.

The other end of the bore 'I2 is counterbored as at 8| to provide a tapered or conical shoulder 2 against which is seated a ball check 83. The ball 83 is resiliently maintained in sealing engagement with the bore 'I2 Vby means of a coil spring 84 which is seated in a cylindrical ball stop element 85 which is secured in the bore 8l.V

The channel 38 in the cap 25, which is plugged as at 86, has a vertical portion 8l which com- Vmunicates with the bore 8| of the check valve vthrough the element 85.

It will be noted that when the piston 'I6 Vis in its uppermost position, as seen in Fig. 4, the end or the stem 'I'I terminates slightly above the ball 83.

As best seen in Figs. 1, 8 and 9, the channel 42 in cap 25 is intercepted by a by-pass channel 88 in the cap which runs horizontally through the cap and has a vertical branch 89 which coin- Vmunicates with a vertical channel 98 in the valve housing 13. The channel 90, in turn, Vhas a laterally extending branch 9| which communicates with the space S in the bore Y'I4 of the check valve assembly, thus interconnecting the space S with the transverse channel 48 in the body 49.

The control valve Projecting laterally from one side of the body 49 is an embossment 94 having a flat face 95 which serves as a mounting surface for a control Valve 96 which communicates with the channels48 and 10.

The valve 96 comprises a valve body 97 having a central longitudinal bore 98 therethrough in which is slidably received a valve stem 99.

The valve is secured to the boss 94 by` means of lead from the bore 98 to spaced vertical channels |05. The channels |05, in turn, communicate with a transverse exhaust channel |06 which is open to atmosphere. Each channel |05 is tapped to receive a thumb screw |01 which can be threadedly adjusted to fully or partially intercept or block the channels |03 and |04 for the purpose of controlling the air flow. In order to retain the thumb screw firmly .in any selected position and to prevent it from being jarred or loosened by vbrations, it is releasably secured by a set screw |08 which is disposed in a tapped opening |09 in the body 91 of the valve.

An inlet channel IIO in the body 91 leads from the bore 98 to an air conduit I I which is threadedly secured to the valve body.

Two axially spaced diametrical openings II2, I I3 are provided in the valve stem 99, which openings are adapted to communicate alternately with the air inlet IIO. Each of the openings |I2,' II3 terminates in an elongated groove or cavity |I4 and II5, respectively,` adjacent the openings II and |02, the groove I I4 being of such dimension as to traverse the channels IOI and |03, and the groove I|5 traversing openings |02 and |04.

At a point on the Valve stem 99 which lies intermediate the openings I|2 and II3, a narrow inclined groove or slot I 6 is provided. The upper end of the slot communicates with the inlet channel I|1 of a gravity oiler II8 which is threadedly secured to the valve body 91. The lower end of the groove I I6 is directed "toward a shallow depression or pocket I I9 which is formed in the wall of the bore 98.

The valve stem 99 ts snugly in the bore 98 and has O-rings I mounted thereon to prevent leakage of air around the stem. Reciprocal slidv ing movement of the valve stem is limited by dog-point set screw I2I which is threadedly secured in the body 91 so as to project into a recess |22 of predetermined length which is provided on the valve stem.

To one end of the valve stem is threadedly secured an extension rod |23 having a knob |24 which facilitates manipulation of the valve stem.

The operation of the device In order to prepare the device for utilization, the plug 8 is removed and a non-compressible fluid such as light oil is poured through the opening 1. The oil fills the portion A of chamber I3 as well as the bore 29 in the stern I1, the channel 38 in the cap 25, and the bore 8| of the check valve. By manually depressing the ball 83, the oil is also caused to flow into channel 1I and thus into cylinders 50. The plug 8 is then replaced so as to close the cylinder I3.

The work-piece which is to be clamped is placed on top of the plunger 6 so that it may be clamped between the plunger and the conventional top plate P which is carried by the standards 3.

In Fig. 6 I have shown the stem of the control valve 96 in a neutral position. If the conduit III be connected to a source of compressed air and the valve stem 99 be moved upwardly (as viewed in Fig. 6), the air will pass through opening I I3 in the valve stem and will be directed by groove I|5 into channels |02 and 10. The air then passes into channels 69 in the body 49 and thence through recess B8 in the cap 64 into the portion C of each of the cylinders 5I.

The pressure on the movable piston 53 causes the piston to be displaced to the right (as viewed in Fig. 3) and the corresponding movement of stem 54 forces the oil in cylinder 50 to flow through channel 1I to bore 12 of the check valve. The oil under pressure raises check valve piston 16 and depresses the ball 83 and flows past the ball into channel 38 in cap 25 and then through opening 4I in stem extension 24 into the bore 29 and thus to the portion A of chamber I3.

Inasmuch as the divider I5 is stationary, the pressure acts upon the closed end I4 of the plunger 6 to elevate it relatively to the divider and thereby clamp the work-piece against the top plate P.

The upward movement of plunger 6 is aided and guided by a guide rod |25 which is secured in a laterally extending ear |26 on the plunger and which is slidably contained in a cylindrical embossment |21 which is provided adjacent the embossment 4.

During the upward movement of the plunger 6, the air which is in the cavity B is forced out through radial opening 31 in the stem I1 and through the annular passageway 36 into channel 42 in cap 25, into channel 48 and thus into channel I0| of the control valve 96 where it is directed by groove II4 into channel |03, channel |05, and exhaust channel |06. The rate at which the air is permitted to exhaust can be controlled by the screw |01 and thus the clamping action of the plunger 6 can be slow or rapid, as desired.

As soon as the plunger 6 has clamped the workpiece, the pressure of the oil on the ball check 83 is equalized and the spring 84 returns the ball to its seat 82 whereby to seal the bore 12 oi the check valve. Thus, if for any reason, the air pressure should iluctuate or fail entirely, the oil in cavity A will still remain under pressure and the plunger 6 will retain the work-piece in clamped position at a uniform pressure.

When the machining operations on. the workpiece have been finished, and it is desired to release the work-piece, the valve stem 99 of the control valve is moved to the position shown in Fig. '7. The compressed air then enters the channels IGI and 48. The air entering channel 48 has three separate, but correlated, functions and takes three paths to accomplish these functions.

Firstly, the compressed air passes from cham nel 48 downwardly thru channel 41 into channel 42 in cap 25, then thru radial opening 43 in stem extension 24 and upwardly through annular passageway 36 and opening 31 into portion B of cavity or chamber I3. The pressure acts on the plug 20 to force the plunger downwardly in the bore 5 and thus release the work-piece.

At the same time, the air flows from channel 42 in cap 25 through bypass channel 89, channel 89, channel 90 in valve housing 13, and through channel 9| into the space S- above the piston 16 in the bore 14 of the check valve. The air pressure acting upon the conical surface forces the piston 16 and its stem 11 downwardly in the cylinder bushing 15 and the stem engages and depresses the ball 83 thereby opening the bore 12 to the return ow of oil from the chamber A. The return ilow of the oil follows in reverse sequence the path heretofore described and thus flows into the reservoir 50 through channel 1I.

The return flow of the oil is assisted and acn celerated by the passage of the compressed air from channel 48 upwardly through channel 93 into the cavity D of bore 5I where it acts upon the piston 53 to move it to the left (as viewed in Fig. 3) as this tends to suck the oil into the reservoir 50.

The air in chamber C of the cylinder 5I is forced out through channel 68, channel 69', ohannel 'I0 and into channel |02 in control valve 96 where it is directed by groove H into channels 101i and |05 and exhausts through channel |55. The rate of exhaust through channel |94 may be controlled by means of the screw |91 in the manner heretofore described.

A resilient ring |28 is provided between the surfaces of the plug and the cap 25 so as to avoid any jarring to the plunger 6 when it reaches the limit of its downward movement. A vent opening |29 in cap 25 prevents any air binding between the cap and the plunger ii.

In addition to the control available through manipulation of the screws |01 on control valve 9B, I also provide means for controlling the flow of oil comprising an element |30 which is threadedly secured in the cap 25 laterally thereof so as to adjustably intercept the channel 38 through which the oil must flow. By adjusting the 'ele ment |30, the rateV of flow of the oil can be controlled. Thus by combining the control functions of the screws |01 and the element |36, I can adjust the operation of the clamping deviceso as to obtain a combination of quick clampingslow release, or quick clampingnquick release, or slow clamping-quick release, or slow clampingslow release.

Leakage of the oil past the element |32 is prevented by an O-ring |3| which is mounted in a recess |32 in the cap 25 and secured therein by means of a nut |33.

As disclosed in my copending application heretofore referred to, the control valve 96 includes novel means for lubricating the wall of bore i2. The groove l I6 on the valve stem Q9 is so disposed that it will collect oil which drips from the oiler H3 into the bore 98 through the inlet iid. As the valve stem is moved from one extreme of position to the other during the operation of the clamping device, a droplet of lubricant from the groove llt collects in the pocket |89. The sudden impingement of the compressed air entering through either channel Y| l2 or H3, as the valve stem is manipulated, causes the lubricant in the pocket to be atomized and carried by the air stream into the cavity I3 where it serves to lubricate the walls of bore I2.

Having thus described my invention, I claimt 1. In a clamping device, the combination of a slidable hollow plunger, a stationary piston corn tained within said plunger, a liquid reservoir, pneumatically actuated means for displacing said liquid from said reservoir and'injecting it into said plunger to displace said plunger relatively to said piston, and means for selectively directing air under pressure into said plunger to displace said liquid and return said plunger to its initial position, said air also being simultaneously die rected against said rst-named means to effect retraction thereof.

2. In a clamping device, the combination of a base, a top plate supported by said base, a clampinGr bar slidably mounted in said base, a iirst fluid motor provided in said base and operatively engaging said clamping bar, a liquid reservoir provided in said base, a iiuid passageway in said base between said reservoir and said first fluid motor, a second fluid motor provided in said base, a rod operatively connected to said second fluid motor and extendinglinto said reservoir, means for directing compressed air into said second uid motor to cause advancement of said rod into said reservoir and responsive advancement of said clamping bar toward said top plate in response tov hydraulic actuation of said iirst fluid motor, and means for directing compressed air simultaneously into said iirst fluid motor and said second duid motor to cause retraction of said clamping bar and concurrent retraction of said rod whereby said iirst fluid motor exerts positive pressure on said liquid and said second iluid motor exerts negative pressure on said liquid to return it to said reservoir.

3. In a clamping device, the combination of a top plate, a clamping bar, a first fluid motor for actuating said clamping bar, said uid motor comprising a rst cylinder, and a iirst piston mounted in said cylinder and deiining two chambers therein, a second fluid motor comprising a second cylinder, and a second piston slidably mounted in said second cylinder and defining two chambers therein, a liquid reservoir, a piston rod Y secured to said second piston and extending into said reservoir, a iuid passageway from said reservoir communicating with one or" said chambers of iirst cylinder, control means for selectively directing compressed air into one of said chambers of said second cylinder to cause said piston rod to advance into said reservoir and displace the liquid therein whereby to actuate said first fluid motor and advance said clamping bar toward said tcp plate, and control means for selectively directing compressed air simultaneously into the other' of said chambers oi" said first and second cylinders to cause retraction of said clamping bar and retraction of said piston rod whereby said liquid is returned tliroughsai-:l pas sageway to said reservoir in response to a positive f pressure thereon in said iirst cylinder and a negative pressure thereon in said reservoir.

4. in a clamping device, the combination of a first cylinder, a iii-st piston mounted in said cylinder and defining two chambers therein, a second cylinder, a second piston slidably mounted in said second cylinder and dening two chambers therein, a liquid reservoir, a piston rod secured to saidjsecond piston and extending into said reservoir, a passageway from said reservoir communicating with one of said chambers of said first cylinder, control means for selectively directing compressed air into one of said chambers of said second cylinder to cause said piston rod to advance into said reservoir and displace the liquid therein whereby said displaced liquid enters said one chamber of said rst cylinder to cause relative movement between said iirst cylinder and said first piston, and control means for selectively directing compressed air simultaneously into the other of said chambers oi said first and second cylinders to cause said liquid to be returned to said reservoir in response to a reversal of movement between said first cylinder and said rst piston and the withdrawal of said piston rod from said reservoir. 

